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Update (2019 Feb 20)

This page was describing an interim procedure that is no longer relevant. We have now made changes to the system to fix the problems/limitations with the 200 MHz correlator, and so we are using that exclusively and no longer need to run the 300 MHz (test) correlator that had been under development. This 300 MHz correlator never worked properly...

Procedure

Note that after switching correlators, or even rebooting ROACHes for a given correlator design, one must determine new delays for each antenna. For unknown reasons, the delays can actually change a LOT on a reboot -- more than just a few steps as expected from the way the ADC works. To get the delays in the ballpark, or at least determine the sign of the delay, observations on CIEL-2 with band23.fsq are extremely helpful. After that, observe a strong phase calibrator for up to 1/2 hour and use delay_widget.py to determine and set the delays.

Switching from 200 MHz to 300 MHz Correlator

Follow these steps, in this order, to switch from a currently running 200 MHz correlator design to a 300 MHz one: